The subject matter disclosed herein relates to a method and apparatus for cleaning dovetails. More specifically, the subject matter disclosed herein relates to a method and apparatus for cleaning dovetails in a dynamoelectric machine.
Conventional dynamoelectric machines, such as generators used with gas and steam turbines, typically employ forged rotors of magnetic material into which radial slots are machined for receiving the conductive turns of field windings that are interconnected such as to produce a desired magnetic flux pattern. Typically, included in such conventional rotor slots are creepage blocks at both the top and bottom ends of the slot as well as coil slot wedges for resisting the radially outward forces exerted on the windings when the rotor is operational. Dovetails are typically located at the top of the radial slots, and may be used in conjunction with slides, wedges and ripple springs that aid in retaining the windings within the radial slots.
The slot wedges, which are generally dovetail shaped, are used to maintain the copper coils or windings in place while the rotor is spinning at, for example, 3600 revolutions per minute. During the lifetime of the rotor one or more re-winding operations may be needed. This process entails removing the windings from the radial slots and either repairing, refurbishing or replacing the windings. The dovetail slots at the top of the radial slots also may need to be cleaned or polished, as the material from the slides, wedges and/or ripple springs can adhere to the surfaces of the dovetail. In addition, negative sequence events (e.g., arcs) can cause fretting. One known method for cleaning the dovetail surfaces requires a worker to manually clean or polish the dovetail. However, this process is labor intensive, time consuming and costly.